Telerik® JustCode™'s unit test runner allows you to run and debug WinJS tests.

Setup your environment

Download qunitmetro.js (found
here).
Then add qunitmetro.js in the "js" folder of your application and add the following code to your startup page (default.html) to setup the QUnitMetro references:
<script src="/js/qunitmetro.js"></script>

Add QUnitMetro.JustCode.js (found in (JustCodeInstallationFolder)/Libraries/Extensions/QUnit/Scripts) in the "js" folder of your application and add the following code to your startup page (default.html) to setup the QUnitMetro references:
<script src="/js/QUnitMetro.JustCode.js"></script>

To Run and Debug Tests from Unit Test Window

From here you can choose how to run or debug your tests from a couple of options:

Run Selected Tests - Select the tests you want to run from the tree and click the button.

Run All Tests - Click the button to run all tests inside your solution.

Debug Selected Tests - Select tests that you want to debug from the tree and click the button.

Once you've run a test, JustCode will start your application in a simulator and a progress bar will be shown to indicate how many tests are currently running.
Also a busy indicator is shown next to currently running test, the class and namespace it's defined in.
Once all test are run JustCode will automatically close the application (but not the simulator).

You can click the button to abort a test run.

As soon as all tests have been run, results are shown on the right side.

To Run and Debug Tests from Solution Explorer Window

Open the Solution Explorer Window.

From the solution tree select the item that contains the unit tests you would like to run.

This item can be either a solution folder, project, folder or a single file.